a) Field of the Invention
The invention is directed to a device for generating extreme ultraviolet (EUV) radiation. The device contains a discharge chamber which has a discharge area for a gas discharge in order to form a plasma that emits the radiation, a first electrode and a second electrode which are electrically separated from one another by an insulator with dielectric rigidity, an outlet opening which is provided in the second electrode for the radiation emitted by the plasma, and a high-voltage power supply for generating high-voltage pulses for the two electrodes.
Further, the invention is directed to a method for generating extreme ultraviolet (EUV) radiation in which a plasma emitting the radiation is generated in a discharge area of a discharge chamber from a source material for an electric discharge by means of gas discharge.
b) Description of the Related Art
Radiation sources which are based on plasmas generated by gas discharge and rely on various concepts have already been described many times. The principle common to these devices consists in that a pulsed high-current discharge of more than 10 kA is ignited in a gas of determinate density and a very hot (kT>30 eV) and dense plasma is generated locally as a consequence of the magnetic forces and the dissipated power in the ionized gas.
Further developments have aimed above all to solutions characterized by a high conversion efficiency and a long life of the electrodes. The problems to be solved stem in part from the dilemma that increasing the distance between the plasma and electrodes, which has a positive effect on the life of the electrodes, leads to reduced efficiency of the collector optics because of the resulting increase in generated plasma, so that there is a reduction in overall efficiency with respect to the power achieved at the intermediate focus for the applied electrical input power for the discharge.
It has been shown that the radiation outputs which were still not sufficient heretofore for lithography using extreme ultraviolet radiation apparently can only be further increased significantly by means of efficient emitter substances such as tin or lithium or combinations thereof (DE 102 19 173 A1).
Tin and lithium have the substantial disadvantage of a high level of debris, so that the collector optics used for bundling and deflecting the EUV radiation are subject to increased contamination.
DE 102 19 173 A1 already addresses the technical problem that when metal emitters are used very high temperatures of the discharge source are required for vaporization and a condensation of the metal vapors inside the source must be prevented if malfunction is to be avoided.